You can vote any way you want to.
You can vote for the party that best reflects your personal views. You can vote for the party with the coolest logo. You can vote for the party best able to beat the party you detest.
You can vote for the person! You can vote for the person who is best qualified (whatever that means). You can vote for your friend, just because she's your friend!
You can flip a coin. You can choose the alphabetically first candidate. You can draw a happy face in all the circles. You can spoil your ballot. You can even refuse it! (Go up to the poll clerk, take your ballot, then say "I refuse it!". They will count it as refused.)
It's up to you. Don't let anyone tell you there's a right way to vote. You don't have to vote your heart. You don't have to be practical and choose the lesser of two evils.
Still, the act of voting has consequences. Happily, these are small for any one voter. (Nobody is going to blame me personally for Bob Rae. Or, maybe they'll blame me, but they won't sue me.)
Still, let's consider. Suppose on the ballot are three names: Margaret Thatcher, Elizabeth May, and Adolf Hitler. You definitely prefer Elizabeth May to Margaret Thatcher, and this Hitler guy just freaks you out -- who would vote for that idiot? But to your surprise and horror, he has been endorsed by major newspapers, and a couple of polls have come out putting him in the lead! The sensible people prefer Margaret Thatcher, and you find Elizabeth May standing all by herself on a street corner handing out pamphlets which nobody will take.
Under these conditions, which, except for the anachronism, are not at all fanciful, it would be irrational and indeed immoral not to vote strategically -- that is, to vote for Margaret Thatcher when you prefer Elizabeth May. There is simply no question. (There are practical problems of judging who in fact would best be able to beat Hitler, but no moral ones.)
Let's consider the opposite case, again three names: Elizabeth May, and two brothers, Tweedledum, and Tweedledee (of the Tweedledumlicans and Tweedledeemocrats, as they were known in my youth). Tweedledum and Tweedledee are identical but insist they are different. They are both boring, unimaginative, and not especially competent. But people love them.
Then, by all means, vote for Elizabeth May. Hope that enough people are encouraged by your example to join you and maybe there will be a surprise. Even if she loses, it may give a salutary scare to the brothers. One of them may start listening. He may steal your ideas, but that's okay. And there's always next time.
Now I am sorry I brought Hitler into this! It rather overweights the argument. Let it stand. But let's try substituting George Bush for Hitler. Bush is an idiot. Thatcher was at least competent. Thatcher might be preferable to Bush, but could I bring myself to vote for her? I don't know that I could, even though I want to prove it is the rational, the prudential thing to do. I might prefer to watch the shambles unfold, and feel smugly that I was right: Elizabeth could not have been worse. This is complicated.
Anyway. This is a roundabout way of imploring any voters who might read this (and who detest Harper) to please, please, please, DON'T let him have a majority. If the votes shifted in sufficient numbers we might see a parliament of almost the same composition as the last. And that would vex Mr. Harper no end -- we might see the proverbial heads exploding. That would be something worth voting for!